Production of glutaric acid



Patented July 4, 1 950 I Richard R. Whetstone, Berkeley, Calif.,assignor to Shell Development Company, San Francisco, QalifJ,acorporation of Delaware v L No. Drawing. ApplicationlMay 25,1948,

' serial No. 29,202v J U This invention relates to the oxidationoffalphahydroxyadipaldehyde to form glutaric acid.

An object of the present'invention'is to oxidizealpha-hydroxyadipaldehyde' to selectively rorm glutaric acid. Anotherobject is to obtain glutaric acid in high yields by the 'directoxidationof alpha-hydroxyadipaldehyde. Yet another object of theinvention is a novel and improved method for the production of glutaricacid. Further objects'of the invention will become apparent hereinafter.

It unexpectedly has been discovered in accord ance with the inventionthat glutaric acid'maybe produced idexoellentyields by oxidizing anaqueous solution of alpha-hydroxyadipaldehyde by treatment with hydrogenperoxide; It has been surprisingly discovered that theglutaric acidmaybe produced as substantially. the only non-volatile organic product ofthe oxidation; a consequence of this discovery, the glutaric acid may beobtained in advantageously high yields-from thealpha-hydroxyadipaldehyde, the yields generally being in the order of.80% or more, based upon the amount of alpha-hydroxyadipaldehyde employedin the execution ofthe process.

The formation of glutaric-acid'and the high yields of this compoundthatahave been obtained, were unexpected results of the-processof, theinvention. The results of the extensive'study of oxidation of organiccompounds with hydrogen peroxide described by .Milas, in,;.Br,itishPatent 508,526, would suggest that aldehydes containing a hydroxyl groupin the alpha position relative toa formyl, group would, upon oxidationwith hydrogen peroxide, 'form the alpha liydroxy carbox'ylic acidcontaining thesame number ,of carbon atoms as the hydroxy aldehyde. -.The patent would not have enabled oneqto foretell that the oxidation ofalpha-hydroxyadipaldehyde according to the process of the; presentinvention would lead to the formation of glutaric acid instead.

Because the glutaric acidis produced in the o ssor the pres ntinventionzitubs ti lly the only non-volatile organic product of theoxidation, theprocess is advantageous relative to prior art processesinwhicha-plurality of nonvolatile organic products including glutaric.;acid is produced. For examplei-it-willjgbe found that the non-volatileproducts obtheflxidation in the present case generally containtheglutaric acid in a sufllcientdegree of purity to enable its utilizationdirectly in various applications without requiring purification of thecrude non-volatile oxidation products. On the 'other hand, if it :isde-' sired to further purify th'e'glutaricacid-produced by the processofthe invention, the purification may be carried out very eflicientlybecause of the absence of undesirably large amounts of nonvolatileorganic products of side reaction.

The oxidation of the alpha-hydroxyadipalde- 3 Claims. (01. 260-530) 7hyde may be efiected in accordance with the invention by mixing, in oneor a plurality of operations, or in a continuous manner, hydrogenperoxide in a suitable amount with an aqueous solution of thealpha-hydroxyadipaldehyde. A convenient form of hydrogen peroxide is theapproximately 30% aqueous solution of commerce. However, moreconcentrated solutions may be employed, to and including even thesubstantially pure hydrogen peroxide thatis becoming available on acommercial scale. 'Aqueous solutions of, hydrogen peroxide lessconcentrated than the 30%v solution may be used, although lessdesirably; For example, even the dilute, or about 3% aqueoussolution ofhydrogen peroxide that is commercially available may be v employed,although the rate of oxidation may be retarded somewhat by therelatively low volume concentration of the oxidizing agent in thereaction mixture. The approximately 30% aqueous solution of hydrogenperoxide is preferred.

f The alpha hydroxyadipaldehyde may be prepared advantageously byhydrolyzing in a neu-' tral to acidic solution, 3,4-dihydro-L2-pyran-2-carboxaldehyde, asdescribed in the copencling application, Serial No.694,144, filed August 30, 1946. The hydrolysis of the formyldihydropyr'an may be carried-out as an operation separate fromand'preceding the-oxidation of the alpha -hydroxyadipaldehyde, or thehydrolysis and the oxidation of the hydrolysis product may be effectedsimultaneously, as by treating the formyl dihydropyran or aqueous,preferably acidic, mixtures containing it and thealphaliydroxyadipaldehyde with neutral or acidulatedsolutions ofhydrogen peroxide. It is preferred to employ the neutral to acidicaqueous solution of alpha-hydrqxyadipaldehyde obtained by the hydrolysisof the 3,4 dihydr01,2-pyran-2-c-arboxaldehydeand containing from about15 to about by'weight of 'alpha-hydroxyadipalde hy'de.

*jfllieoxidation may be efiected by adding hydrogen peroxide to theaqueous solution of alphahydroxyadipaldehyde or'by otherwise'mixing thetwo'materials. The amount of hydrogen peroxide should-be notsubstantially less than theamount temperature range, say from 60 C. to80 C. The

cycle may be repeated in the event the hydrogen peroxide is added in a,plurality oi portions. If

excessive amounts of heat .areevolved' ithe.re-

action mixture may be cooled as'required,-.ori the rate of heatevolution may be controlled by regu lation of the rate of additionof'-the "hydi ogen" Other expedientsfor peroxide to the mixture.regulating the temperature of the reactin..mix'- ture will be apparenttoj those skilled in the art toyvhich theinventionpertains. v

T'The oxidation reaction startssmoothly and spontaneously .upon .mixingof the solutionof alphaehydroxyadipald'ehyde i and. the Lliydrogenperoxide. .It .is.not..necess& y to .gemp1oy;cat+

alyststo eiieet .the desired reaction; howeyerin its generic concepts.the inventionldoes notv exclude .the presenceof catalysts, e. g.,suitable nietal.salts,in.the reaction mixture.

It .has. been observed; that .in the execution of. the-processof-thepresentinvention, the .reaction .mixture,.. and hence. the brudeglutaricacid produced by. the. process, is colorless, that is, Water white,ordevoid of. color-producing bodi'es. Accordingly, .when. the oxidationis completed acrude glutaricacidof high quality .with respect tocolor(or freedom from color) mayibe obtained simplyby evaporatingoif .theWater to leave the :crude solids. Anysuitableevaporator, e. g., a vacuumevaporator, of types Well-known to the art may-nbe employed. .Ifdesired, the evaporation inaybe :interrupted, priorv to v.completeremoval of the water and glutaricacid .al-,

lowed to crystallize from-the partially, evapo;

ratedsolution. The purityof the crude.proolv uct issuchthata,-s-ingle,recrystallization-from. a

suitable-organic solvent, e.- g., ;benzene,; generally afiordsa. .finalproduct=lhaving a rnelting point in..excellent agreement with themelting point'oi'highly refined glutaric acid. 1 The followinglexamplewill illustrate the in,- vention'. It will be understood that theexample is-intended to -.be only illustrative andthat the inventionincludes the-equivalents and'modifications. thereof that-are-Withinthescope otthe appended claims. v l Example Y A mixture of 267 partsbywaged. 3,4-dihydroa1,2-pyran 2. carboxa1dehyde With.560 parts byweight of Q0216 normal. sulfuric acid .solution (aqueous) was held atroom temperature for'2 /2 hours. An :excess of calcium carbonatethen'was addedto neutralize theiacid and the mixture filtered. Tothe.filtrateycontainingflah pha-hydroxyadipaldehyde (about 90% basedonthe -formy1: dihydropyranemployed) there was added 'SiO; partsoiaqueoushydrogen per- I oxide solution i-nsixequal: portions-at regularformyl dihydropyran employed. The crude product ass-purifiedby;.filtration of a, solution tlz crfi i. nf i hi'vil l-1; ir i li e hether, and crystallization of the residue from benzene. qafter onerecrystallization from benzene the product melted at 97 C., the valuereported in the literature-for the melting point of glutaric acid,Yie1d.of.purified product: 242 parts, correspondingato -conversion tothe acid of 77%. i0. n lxclaimwas myzinvention:

. l. Inaprocess for the production of glutaric xi'acid adding inaplurality of increments to an ad ous solution ofalpha-hydroxyadipa1dehyde amaque'ous solution of hydrogen peroxidehaving a concentration of; hydrogen peroxide of about-30%{by-weight;inan amount corresponding to fromabout 3 toaboutf5 inoles. of hydro,- gen-.-peroxide; :per;-mole;of alpha hydroxyadi-paldehyde attemperatureswithin the-range of .from C ."to;"90' C; and continuing. the ensuingre-. action for a';.time-rsuchthat: appreciable and substantialquantities of glutaric acid areiormed. in thereaction. mixture and thenterminating the reaction.

H 2.. In :therproduction of glutaricacid, .theimprovement whichcomprises mixing an aqueous solution of alphaehydrexyadipaldehyde and anaqueous s'olutionl of hydrogen peroxide having a concentration 20fhydrogen: {ZQQIQ-Xidt) 1 of about 3c%,aby "Weight,youth-temperatureswithin the range of fromwabout: :40.- -C. *to about '90 C. in

amounts "corresponding-to 'fromabout '25- to.

about" 5 moles'cot "hydrogen peroxide. per -mole 3 0f=,alpha-hydroxyadipaidehyde, and ,--.continuing range for a time such-that appreciable and substantial quantities of-tzfglutairic acid f are:formed inthe reaction mixturaaa'nd recovering thejglutari-cacidirom'thelre'sultingmixture.

3. In the'rpro'ductidn zofjfglutaric acidiithe .ime provemehtwvhiclrriconiprisies mixing an aqueous solution 1 of alp'hahydroxya'dipaldehydeand aqueous 'hydrogenoperoxide "having- -'a sconcen tration"not' lssthanizabout 3%, by weight, of hydrogen peroxide; temperatures Within therange offrom abou of'fthe reacti 'n; mixture amounts correspondin to notiess' than about 2.5 m'oles of hydrogen peroxide" -'per m'ole i ofalpha' hydroxyadipaldeh'yd'e, --"-ari'd' continuing the ensuing.reaction at temperatures "iyithir'i said iange'for such .a timethatappreciable and substantial quantities of glutari'c" acid 'are"iorfiied in the reaction i'nixtur'e.

Brennan R. *Wl-IETSTONE. rREfiEhENCEd0i-TED Q rncesere of record in thethe ensuing reaction at temperatures within said C.'up totheboiling'point

3. IN THE PRODUCTION OF GLUTARIC ACID, THE IMPROVEMENT WHICH COMPRISESMIXING AN AQUEOUS SOLUTION OF ALPHA-HYDROXYADIPALDEHYDE AND AQUEOUSHYDROGEN PEROXIDE HAVING A CONCENTRATION NOT LESS THAN ABOUT 3%, BYWEIGHT, OF HYDORGEN PEROXIDE, AT TEMPERATURES WITHIN THE RANGE OF FROMABOUT 20*C. UP TO THE BOILING POINT OF THE REACTION MIXTURE IN AMOUNTSCORRESPONDING TO NOT LESS THAN ABOUT 2.5 MOLES OF HYDROGEN PEROXIDE PERMOLE OF ALPHA-HYDROXYADIPALDEHYDE, AND CONTINUING THE ENSUING REACTIONAT TEMPERATURES WITHIN SAID RANGE FOR SUCH A TIME THAT APPRECIABLE ANDSUBSTANTIAL QUANTITIES OF GLUTARIC ACID ARE FORMED IN THE REACTIONMIXTURE.